Diameter protocol is a kind of protocol widely applied in PCC (Policy and Charging Control, policy and charging control) architecture and an LTE (Long Term Evolution, long term evolution) of a 3G network, and an IMS (IP Multimedia Subsystem, IP multimedia subsystem) network. DRA (Diameter Routing Agent, Diameter message routing agent) is used for providing a Diameter signaling message routing function, and is deployed to form a next generation signaling network. DRA can achieve centralized forwarding of Diameter signaling in a multi-network architecture, which includes GPRS (General Packet Radio Service, general packet radio service) or EPC (Evolution Packet Core, evolved packet core), as well as mobility management, policy charging and charging information of a user in a PCC network.
In a PCC system, PCEF (Policy and Charging Enforcement Function, policy and charging enforcement function) entity is routed to PCRF (Policy and Charging Rule Function, policy and charging rule function) entity by DRA, and AF (Application Function, application function) entity is also routed to PCRF by DRA. Specifically, as for routing from the PCEF to the PCRF, the DRA makes routing analysis with a user's IMSI (International Mobile Subscriber Identification Number, international mobile subscriber identity); as for routing from the AF to the PCRF, because there is no user's IMSI in the routing request transmitted by the AF, then the DRA makes routing analysis with a user's IP address. The DRA needs to record corresponding relationship between an IP address and an IMSI of the same user, so as to guarantee that AF and PCEF of the same user can be routed to the same PCRF.
In order to improve reliability of signaling network networking, biplane networking can be used, that is, more than two DRAs can be used, where one or more DRAs act as a backup of another DRA or load sharing of more DRAs, so that signaling service cannot be affected even if one of DRAs goes wrong. However, there is only a method for determining a PCRF by an DRA in a scenario of monoplane networking provided in the prior art, and thereby a solution for determining a PCRF by an DRA in a scenario of biplane networking is strongly demanded.